When Jamie is singing to a grumpy Cathy after a long day at the bar, the pink dress on the mannequin goes from correctly seem to falling off the mannequin to half on the mannequin.
Towards the end of "Shiksas Goddess", Kathy extends her left hand which Jamie then takes to pull her up, but when the angle changes, he is then pulling her up with her right hand.
When Cathy is singing "Goodbye Until Tomorrow" we are to believe that it is 2008. The license plate of the car outside of her apartment is the current NY state gold and blue design, which wasn't put into effect until 2010.